The present invention relates to a new and improved construction of arc electrode, especially for a contact arrangement employed in a vacuum switch, comprising an essentially hollow cylindrical contact component and electrode elements fixedly connected therewith and protruding into the interior of the contact component, said electrode elements serving to take-up the arc base points.
Such type arc electrode has been disclosed in U.S. Pat. No. 3,866,055, granted Feb. 11, 1975 , corresponding to Swiss Pat. No. 531,784, and the disclosures of which are incorporated herein by reference. Upon opening a vacuum switch equipped with such arc electrodes there initially prevails an arc between the contact surfaces of the contact components, which arc, under the action of the self-magnetic field, commutates from the contact surfaces to the narrow surfaces of the electrode elements and at that location burns in a diffuse manner until extinguishing the arc.
Notwithstanding the fact that in the case of arcs which burn in a diffuse manner the contact burn-off is less than in the case of a column arc, still there are nonetheless formed metallic vapors which do not condense to a sufficient degree in the space formed by the contact component and located behind the electrode elements, and therefore, such vapors at least partially can migrate back into the separation gap or path. Even relatively small amounts of metallic vapors in the separation gap can lead to re-ignition of the arc, thereby appreciably impairing the operational reliability of the switch.
In order to cool and condense such metallic vapors it has already been proposed to arrange in this space or compartment behind the electrode elements a condenser consisting of metallic chips or shavings or sheet metal members.
Such devices however are not adequate in the case of arc electrodes for vacuum switches operating at high cut-off or interruption currents, and additionally, they are complicated and expensive to fabricate.